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I'm currently learning about corrosion prevention, and have a question regarding galvanising.
Say that you have an iron nail. You galvanise it (coat it in zinc), so that is doesn't rust by preventing water and Oxygen from reaching its surface. But then wouldn't the Zinc coating rust? What would be the point of galvanising an object when its coating is going to rust anyway?
Galvanizing isn't just a protective coating in the sense that it avoids contact between the iron and the oxidant. Zinc oxidizes more easily than iron, and since both conduct electricity, you can have zinc in contact with the iron anywhere, and it will oxidize first. The term for zinc in this case is "sacrificial anode."
Full coating does help additionally though, by forming a protective layer of zinc oxide. Iron deteriorates when it rusts, so new iron metal is always being exposed as the process continues. However, some metals form oxides that protect the metal underneath from further oxidation. Zinc and aluminum are both examples of these metals.
